An ozone treatment device is known as an existing water treatment device, but a persistent substance that cannot be removed using an existing ozone treatment device may be included in industrial waste water or the like. In particular, removal of dioxins, a dioxane, and the like, is a considerable problem. In response to this kind of problem, a method whereby a hydroxyl radical (OH), which is more highly active than ozone, is generated in treatment target water by combining ozone (O3) and hydrogen peroxide (H2O2) or ultraviolet light, and removal of a persistent substance is carried out, has been partly put to practical use. However, this method is such that device cost and operating cost are extremely high, and the reality is that the method is not widespread.
Also, a method whereby a hydroxyl radical, or the like, generated by an electrical discharge is caused to act directly on treatment target water, thereby removing a persistent substance, has been proposed as another method. For example, in Patent Document 1, a water treatment system including a multiple of hollow cylindrical discharge electrodes is such that gas is caused to flow in a hollow portion of the discharge electrode, and a gas including a radical obtained by an electrical discharge being carried out in a vicinity of a gas ejection is ejected into treatment target water, whereby a persistent organic substance, or the like, dissolved in the water is treated so as to degrade. Also, a purifying device presented in Patent Document 2 is such that positive and negative electrodes are disposed with spaces between each other in a treatment space, and an electrical discharge is carried out in a state wherein a treatment target article is in contact with one of the electrodes, thereby purifying the treatment target article.